The present invention relates generally to systems for igniting fuel and, more particularly, to a spark ignition apparatus for a gas appliance.
Gas appliances have not extensively used direct spark ignition systems on appliances using microprocessor-based electronic controls to ignite burners because the transient electrical pulses or voltage spikes from known single probe spark ignition systems may undesirably interfere with electronic circuits.
Fuel-connected appliances may comprise a spark ignition system to ignite fuel at a burner. In known single electrode spark ignition systems for appliances, fuel emanates from a burner that is typically grounded to the chassis of the appliance. The chassis, however, may not be properly grounded. For example, the chassis of an appliance may be resting on nonconductive plastic or rubber wheels, or the chassis may be resting on a nonconductive surface such as wood. In order to ignite the fuel, a voltage potential difference is generated between an electrode and the burner. The voltage potential difference may be in the range of 12,000 to 20,000 volts. Consequently, a 12,000 to 20,000 volt ignition spark is generated between the electrode and the burner. An ignition spark of this magnitude may cause transient electrical pulses or voltage spikes to undesirably interfere with the performance of electronic circuitry of the appliance. For instance, the transient electrical pulses or voltage spikes may interfere with the performance of a microprocessor-based or microcontroller-based control circuit of an appliance. The transient electrical pulses or voltage spikes may also reset a microprocessor power supply that typically operates at 5 volts. In addition, the transient electrical pulses or voltage spikes may damage components of electric circuitry, may cause a microprocessor or microcontroller to incorrectly process information, and/or may cause electronic circuitry to lockup or crash.
Due to the shortcomings of known single electrode spark ignition systems when used in conjunction with electronic circuitry, manufacturers of appliances have instead used dual electrode spark ignition systems, hot surface igniters to ignite fuel, and single electrode spark ignition systems with a discrete spark module control isolated from the main microprocessor-based electronic control system. U.S. Pat. Nos. 5,003,960 and 5,033,449 disclose embodiments of a dual electrode spark ignition system. In a dual electrode spark ignition system, a spark is caused to jump from one electrode to another electrode, rather than from one electrode to chassis ground.
In order to prevent transient electrical pulses or voltage spikes from interfering with electronic circuitry, both electrodes of a dual electrode spark ignition system are heavily isolated from chassis ground and the electronic circuitry. For example, U.S. Pat. Nos. 5,003,960 and 5,033,449 utilize a ceramic insulating material to isolate the electrodes. Nevertheless, water, food, grease, or other conductive materials may gather on the insulating materials and short the electrodes to chassis ground and/or the electronic circuit. In addition, cracks may develop in the insulating material. As a result, water, food, grease, or other conductive materials may enter the cracks and short the electrodes to chassis ground and/or the electronic circuitry.
On the other hand, a hot surface igniter may not interfere with the functions of a microprocessor or other electronic circuitry. For example, appliance controls like those to companies such as the General Electric Company, Louisville, Ky., utilize hot surface igniters like those manufactured by Norton Company, Milton, N.H., and such igniters may have three significant shortcomings. First of all, the igniter elements may be made of silicon carbide or other similar fragile materials that may easily break or be damaged during shipment. Secondly, hot surface igniters may have a high field failure rate due to the igniter""s elements burning out. Lastly, hot surface igniters may cost approximately seven times more than a single electrode spark igniter which Is adapted for use in gas cooktops and the surface burners of ranges. Using hot surface igniters, for example, on all four surface burners of gas cooktops or ranges would be too costly and too prone to field failures.
In light of the shortcomings of the above-mentioned systems, a need exists for a reliable and less expensive single electrode spark ignition system that does not damage or interfere with the performance of electronic circuitry.
The present invention provides a spark ignition system for a gas appliance. The spark ignition system of the present invention is less expensive and more durable and reliable than known gas appliance ignition systems, The spark ignition system of the present invention has microprocessing and digital electronic circuits that are not affected by the high voltage sparks required to ignite the fuel. The spark ignition system of the present invention is especially useful over a wide range of gas appliances.
According to the principles of the present invention and in accordance with the preferred embodiments, the invention provides an apparatus having a gas appliance with a burner that emanates fuel for ignition. A spark ignition control has a first common ground plane, a conductive piece disposed adjacent the burner and grounded to the first common ground plane, and a second common ground plane. The spark ignition control further has an electrode disposed in a spark generating relationship to the conductive piece to ignite the fuel, and a P-N junction device electrically connected between the first and second common ground planes. An N-section of the P-N junction device is connected to the first common ground plane, a P-section of the P-N junction device is connected to the second common ground plane.
In an alternative embodiment, the present invention provides an apparatus having a gas appliance with a burner that emanates fuel for ignition. A spark ignition control has only one electrode disposed in a spark generating relationship with the burner to ignite the fuel. The spark ignition control has microprocessing electronic circuits electrically connected to a first common ground, and a high voltage spark circuit electrically connected to a second common ground having an electrical potential different from the first common ground.